U.S. patent application number 14/709949 was filed with the patent office on 2015-11-19 for current control apparatus for three-phase rotary machine.
The applicant listed for this patent is DENSO CORPORATION. Invention is credited to Yasuhiro NAKAI.
Application Number | 20150333686 14/709949 |
Document ID | / |
Family ID | 54539344 |
Filed Date | 2015-11-19 |
United States Patent
Application |
20150333686 |
Kind Code |
A1 |
NAKAI; Yasuhiro |
November 19, 2015 |
CURRENT CONTROL APPARATUS FOR THREE-PHASE ROTARY MACHINE
Abstract
In an apparatus, a synchronizing unit synchronizes a measurement
timing of values of first and second phase currents by a current
sensor with a measurement timing of a rotational angle of a rotor
by a rotational angle sensor. A current calculator calculates,
based on the first and second parameter signals and the rotational
angle of the rotor, values of two phase currents in a rotational
coordinate system defined with respect to the rotor. A transmitter
transmits the values of the two phase currents using a
communication protocol. A controller communicates with the
transmitter using the communication protocol to receive the values
of the two phase currents. The controller controls the first phase
current, the second phase current, and a third phase current
flowing through respective first, second, and third phase windings
of a three-phase rotary machine according to the values of the
two-phase currents.
Inventors: |
NAKAI; Yasuhiro;
(Kariya-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DENSO CORPORATION |
Kariya-city |
|
JP |
|
|
Family ID: |
54539344 |
Appl. No.: |
14/709949 |
Filed: |
May 12, 2015 |
Current U.S.
Class: |
318/400.26 ;
318/400.37 |
Current CPC
Class: |
G01D 5/2073 20130101;
H02P 21/22 20160201; H02P 27/08 20130101; H02P 21/06 20130101; H02P
6/12 20130101; H02P 27/06 20130101 |
International
Class: |
H02P 27/06 20060101
H02P027/06; H02P 6/12 20060101 H02P006/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 13, 2014 |
JP |
2014-099196 |
Claims
1. An apparatus for controlling a three-phase rotary machine
including first, second, and third phase stator windings, the
apparatus comprising: a current sensor that measures values of
first and second phase currents respectively flowing through at
least the first and second phase windings of the three-phase rotary
machine, and outputs first and second parameter signals, each of
the first and second parameter signals representing the measured
value of a corresponding one of the first and second currents; a
rotational angle sensor that measures a rotational angle of a rotor
of the three-phase rotary machine; means, connected to the current
sensor and the rotational angle sensor, for synchronizing a
measurement timing of the values of the first and second phase
currents for the current sensor with a measurement timing of the
rotational angle of the rotor for the rotational angle sensor; a
current calculator that calculates, based on the first and second
parameter signals and the rotational angle of the rotor, values of
two phase currents in a rotational coordinate system defined with
respect to the rotor; a transmitter that transmits the values of
the two phase currents calculated by the current calculator in
accordance with a predetermined communication protocol; and a
controller that communicates with the transmitter in accordance
with the predetermined communication protocol to receive the values
of the two phase currents, and controls the first phase current,
the second phase current, and a third phase current flowing through
the respective first, second, and third phase windings according to
the values of the two-phase currents.
2. The apparatus according to claim 1, wherein: the rotational
angle sensor is a resolver that: measures, based on a sinusoidal
excitation signal, a first AC signal and a second AC signal, the
first and second AC signals having a phase shift of 90 electrical
degrees therebetween; and outputs at least the first AC signal and
the second AC signal; and the current calculator comprises a
resolver/digital converting unit that receives at least the first
AC signal and the second AC signal, and converts the first AC
signal and the second AC signal into the rotational angle of the
rotor.
3. The apparatus according to claim 1, wherein the transmitter is
configured to transmit the rotational angle of the rotor measured
by the rotational angle sensor to the controller in accordance with
a predetermined communication protocol.
4. The apparatus according to claim 2, wherein the transmitter is
configured to transmit the rotational angle of the rotor measured
by the rotational angle sensor to the controller in accordance with
a predetermined communication protocol.
5. The apparatus according to claim 2, further comprising: an
inverter having a housing and converting DC power to AC power and
applying the AC power to the three-phase windings of the
three-phase rotary machine, wherein: the controller is configured
to control the inverter based on the values of the two-phase
currents, thus controlling the first phase current, the second
phase current, and the third phase current flowing through the
respective first, second, and third phase windings; at least the
synchronizing means, the current calculator, and the transmitter
are installed in the housing of the inverter; the controller is
located outside the housing of the inverter; and the transmitter is
configured to transmit at least the values of the two phase
currents calculated by the current calculator to the controller in
accordance with the predetermined communication protocol.
6. The apparatus according to claim 3, further comprising: an
inverter having a housing and converting DC power to AC power and
applying the AC power to the three-phase windings of the
three-phase rotary machine, wherein: the controller is configured
to control the inverter based on the values of the two-phase
currents, thus controlling the first phase current, the second
phase current, and the third phase current flowing through the
respective first, second, and third phase windings; at least the
synchronizing means, the current calculator, and the transmitter
are installed in the housing of the inverter; the controller is
located outside the housing of the inverter; and the transmitter is
configured to transmit at least the values of the two phase
currents calculated by the current calculator to the controller in
accordance with the predetermined communication protocol.
7. The apparatus according to claim 4, further comprising: an
inverter having a housing and converting DC power to AC power and
applying the AC power to the three-phase windings of the
three-phase rotary machine, wherein: the controller is configured
to control the inverter based on the values of the two-phase
currents, thus controlling the first phase current, the second
phase current, and the third phase current flowing through the
respective first, second, and third phase windings; at least the
synchronizing means, the current calculator, and the transmitter
are installed in the housing of the inverter; the controller is
located outside the housing of the inverter; and the transmitter is
configured to transmit at least the values of the two phase
currents calculated by the current calculator to the controller in
accordance with the predetermined communication protocol.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on and claims the benefit of
priority from Japanese Patent Application No. 2014-099196 filed on
May 13, 2014, the disclosure of which is incorporated in its
entirety herein by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to current control
apparatuses for a three-phase rotary machine, and more
particularly, to such current control apparatuses capable of
controlling a current flowing through each phase winding of a
three-phase rotary machine.
BACKGROUND
[0003] A known inverter has the ability to control currents flowing
through respective three-phase windings of a three-phase motor as
an example of three-phase rotary machines. Specifically, a
controller of the known inverter obtains actual values of at least
first and second currents flowing through corresponding at least
first and second phase windings of the three-phase motor using
current sensors provided for the corresponding first and second
phase windings. The controller also measures an actual rotational
angle of a rotor of the three-phase motor using a rotational angle
sensor. The known inverter is disclosed in Japanese Patent
Application Publication No. 2013-118746, which will be referred to
as a patent document 1.
SUMMARY
[0004] The controller of the inverter disclosed in patent document
1 will be described in more detail hereinafter. Specifically, the
controller of the inverter receives the actual values of the at
least first and second phase currents obtained by the corresponding
current sensors, and receives the actual rotational angle of the
rotor measured by the rotational angle sensor. Then, the controller
transforms, using the actual rotational angle of the rotor received
thereby, the actual values of the at least first and second phase
currents received thereby into values of two-phase currents in a
two-phase rotating coordinate system defined relative to the rotor.
The controller controls a switching circuit of the inverter to
alternately switch a current conduction and a current interruption
between a voltage source and each phase winding via the switching
circuit. The control of the switching circuit adjusts a value of
each of the two-phase currents to match with a target value
predetermined for a corresponding one of the two-phase
currents.
[0005] The transforming of the actual values of the respective at
least first and second phase currents to values of the two-phase
currents in the two-phase rotating coordinate system requires the
actual rotational angle of the rotor measured by the rotational
angle sensor. There may be a gap between the timing when the
controller receives the actual values of the respective at least
first and second phase currents from the corresponding respective
current sensors and the timing when the controller receives the
actual rotational angle measured by the rotational angle sensor.
The gap may result in reduction in the accuracy of transforming,
based on the actual rotational angle of the rotor, the actual
values of the at least first and second phase currents to values of
the two-phase currents in the two-phase rotating coordinate system.
It is therefore desirable to provide a creative idea to address the
reduction in the transformation accuracy.
[0006] In view of the circumstances set forth above, one aspect of
the present disclosure seeks to provide a current control apparatus
for a three-phase rotary machine, which is designed based on the
creative idea to address the reduction in the transformation
accuracy.
[0007] Specifically, a specific aspect of the present disclosure
aims to provide such a current control apparatus that is capable of
improving the accuracy of transforming actual values of at least
first and second phase currents into value of two-phase currents in
a two-phase rotating coordinate system defined in a rotor.
[0008] According to an exemplary aspect of the present disclosure,
there is provided an apparatus for controlling a three-phase rotary
machine including first, second, and third phase stator windings.
The apparatus includes a current sensor that measures values of
first and second phase currents respectively flowing through at
least the first and second phase windings of the three-phase rotary
machine, and outputs first and second parameter signals, each of
the first and second parameter signals representing the measured
value of a corresponding one of the first and second currents. The
apparatus includes a rotational angle sensor that measures a
rotational angle of a rotor of the three-phase rotary machine. The
apparatus includes a synchronizing unit, connected to the current
sensor and the rotational angle sensor, for synchronizing a
measurement timing of the values of the first and second phase
currents for the current sensor with a measurement timing of the
rotational angle of the rotor for the rotational angle sensor. The
apparatus includes a current calculator that calculates, based on
the first and second parameter signals and the rotational angle of
the rotor, values of two phase currents in a rotational coordinate
system defined with respect to the rotor. The apparatus includes a
transmitter that transmits the values of the two phase currents
calculated by the current calculator in accordance with a
predetermined communication protocol. The apparatus includes a
controller that communicates with the transmitter in accordance
with the predetermined communication protocol to receive the values
of the two phase currents. Based on the values of the two-phase
currents, the controller controls the first phase current, the
second phase current, and a third phase current flowing through the
respective first, second, and third phase windings.
[0009] The synchronizing unit of the apparatus synchronizes the
measurement timing of the values of the first and second phase
currents for the current sensor with the measurement timing of the
rotational angle of the rotor for the rotational angle sensor.
[0010] This synchronization results in calculation of values of the
two phase currents for the current calculator with higher accuracy
in comparison to calculation of values of the two phase currents in
a case where the measurement timing of the values of the first and
second phase currents for the current sensor is asynchronous with
the measurement timing of the rotational angle of the rotor for the
rotational angle sensor.
[0011] The transmitter of the apparatus transmits the values of the
two phase currents calculated by the current calculator in
accordance with the predetermined communication protocol. The
controller communicates with the transmitter in accordance with the
predetermined communication protocol to receive the values of the
two phase currents. Based on the values of the two-phase currents,
the controller controls the first phase current, the second phase
current, and a third phase current flowing through the respective
first, second, and third phase windings. Thus, even if the
apparatus is configured to transmit the values of the two phase
currents to the controller in accordance with the predetermined
communication protocol, the apparatus results in proper control of
the three-phase currents flowing through the respective three-phase
windings of the three-phase rotary machine.
[0012] The above and/or other features, and/or advantages of
various aspects of the present disclosure will be further
appreciated in view of the following description in conjunction
with the accompanying drawings. Various aspects of the present
disclosure can include and/or exclude different features, and/or
advantages where applicable. In addition, various aspects of the
present disclosure can combine one or more feature of other
embodiments where applicable. The descriptions of features, and/or
advantages of particular embodiments should not be construed as
limiting other embodiments or the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Other aspects of the present disclosure will become apparent
from the following description of embodiments with reference to the
accompanying drawings in which:
[0014] FIG. 1 is a circuit diagram schematically illustrating an
example of the structure of a current control apparatus according
to an embodiment of the present disclosure;
[0015] FIG. 2 is a circuit diagram schematically illustrating an
example of the structure of a current control apparatus according
to a comparative example of the embodiment;
[0016] FIG. 3 is a timing chart schematically illustrating
measurement timings of values of first and second analog voltage
signals from a motor-generator, and measurement timings of values
of respective sinusoidal excitation signal, first sinusoidal AC
signal, and second cosine AC signal from the motor-generator
according to the comparison example;
[0017] FIG. 4 is a graph schematically illustrating how V- and
W-phase currents change over time, and an angle of a rotor of the
motor-generator changes over time;
[0018] FIG. 5 is a graph schematically illustrating a phase shift
of a current vector based on values of d- and q-axis currents in a
d-q coordinate system due to sampling-timing asynchronous occurred
in a current control system according to the comparative
example;
[0019] FIG. 6 is a block diagram schematically illustrating an
example of the structure of an IC illustrated in FIG. 1; and
[0020] FIG. 7 is a timing chart schematically illustrating
measurement timings of values of first and second analog voltage
signals from the motor-generator, and measurement timings of values
of respective sinusoidal excitation signal, first sinusoidal AC
signal, and second cosine AC signal from the motor-generator
according to the embodiment.
DETAILED DESCRIPTION OF EMBODIMENT
[0021] A specific embodiment of the present disclosure will be
described hereinafter with reference to the accompanying
drawings.
[0022] A current control apparatus 10 for controlling a
motor-generator (MG) 11, which is an example of a three-phase
rotary machines, embodies one aspect of the present disclosure as a
specific embodiment. The current control apparatus 10 and the
motor-generator 11 are for example installed in a motor vehicle,
such as a hybrid vehicle or an electric vehicle.
[0023] First, an example of the structure of the current control
apparatus 10 for the motor-generator 11 will be described
hereinafter with reference to FIG. 1.
[0024] The current control apparatus 10 includes an inverter 12,
and an electronic control unit (ECU) 13 for controlling the
motor-generator 11; the motor-generator 11 is illustrated as MG ECU
in FIG. 1. The current control apparatus 10 also includes a
resolver 45 that is an example of rotational angle sensors.
[0025] The motor-generator 11 is coupled to driving wheels of the
motor vehicle, and serves as a main engine of the motor vehicle.
Specifically, the motor-generator 11 is operative to generate
torque for rotatably driving the driving wheels of the motor
vehicle. For example, the motor-generator 11 is a three-phase
permanent magnet synchronous motor-generator.
[0026] The motor-generator 11 is provided with a rotor and a stator
(not shown). The rotor is provided with at least one pair of
permanent magnets. The rotor has a direct axis (d-axis) in line
with a direction of magnetic flux created by an N pole of the at
least one pair of permanent magnets. The rotor also has a
quadrature axis (q-axis) with a phase being .pi./2-radian
electrical angle leading with respect to a corresponding d-axis
during rotation of the rotor. In other words, the q-axis is
electromagnetically perpendicular to the d-axis (see FIG. 5
described later).
[0027] The d and q axes constitute a d-q coordinate system, i.e. a
two-phase rotating coordinate system, defined relative to the
rotor.
[0028] The stator includes a stator core such that the rotor is
rotatably arranged with respect to the stator core. The stator also
includes a set of three-phase windings, i.e. armature windings,
wound in the stator core.
[0029] The three-phase, i.e. U-, V, and W-phase, stator windings
are wound in the stator core such that the U-, V-, and W-phase
windings are shifted by an electrical angle of, for example,
2.pi./3 radian in phase from each other.
[0030] For example, the three-phase stator windings, i.e. U-, V-,
and W-phase windings, each have a first end connected to a common
junction, i.e. a neutral point, and a second end, opposite to the
first end, serving as a separate terminal. That is, the three-phase
stator windings are connected to each other to have a
star-configuration.
[0031] Specifically, the motor-generator 11 functions
[0032] (1) As a motor to generate torque, i.e. motion power, for
rotatably driving the driving wheels
[0033] (2) As a generator to generate electrical power.
[0034] The torque generated by the motor-generator 11 turns the
driving wheels of the motor vehicle, thus causing the motor vehicle
to run.
[0035] A DC power source 40 is connected to the motor-generator 11
via the inverter 12. The DC power source 40 is configured to
transfer electrical power therefrom to the motor-generator 11 via
the inverter 12, and receive electrical power transferred from the
motor-generator 11 via the inverter 12.
[0036] The inverter 12 is designed as a three-phase inverter.
Specifically, the inverter 12 includes a housing 12a, a switching
circuit 21, first and second current sensors 41 and 42, and an
integrated circuit (IC) 30. The elements 21, 41, 42, and 30 are
installed in the housing 12a. The first and second sensors 41 and
42 are illustrated in some of the drawings as Iv sensor and Iw
sensor.
[0037] The switching circuit 21 includes a first pair of
series-connected high- and low-side (upper- and lower-arm)
switching elements Sup and Sun, a second pair of series-connected
high- and low-side switching elements Svp and Svn, and a third pair
of series-connected high- and low-side switching elements Swp and
Swn. The switching circuit 12 also includes flywheel diodes Dup,
Dun, Dvp, Dvn, Dwp, and Dwn electrically connected in antiparallel
to the respective switching elements Sup, Sun, Svp, Svn, Swp, and
Swn.
[0038] The first to third pairs of switching elements are parallely
connected to each other in bridge configuration.
[0039] As the switching elements S*# (*=u, v, and w, and #=p and
n), IGBTs, MOSFETS, or bipolar transistors can be respectively
used. When MOSFETs are used as the switching elements S*#,
intrinsic diodes of the power MOSFETs can be used as the flywheel
diodes, thus eliminating the need for external flywheel diodes.
[0040] A connection point, through which the switching elements Sup
and Sun of the first pair are connected to each other in series, is
connected to the separate terminal of the U-phase winding via a
U-phase cable Cu. Similarly, a connection point, through which the
switching elements Svp and Svn of the second pair are connected to
each other in series, is connected to the separate terminal of the
V-phase winding via a V-phase cable Cv. Moreover, a connection
point, through which the switching elements Swp and Swn of the
third pair are connected to each other in series, is connected to
the separate terminal of the W-phase winding via a W-phase cable
Cw.
[0041] The star-configuration of the three-phase stator windings
results in the sum of three-phase currents flowing through the
respective cables Cu, Cv, and Cw being zero in accordance with
Kirchhoff's law.
[0042] One end of the series-connected switching elements of each
of the first, second, and third pairs is connected to the positive
terminal of the DC power source 40 via a positive terminal of the
inverter 12. The other end of the series-connected switching
elements of each of the first, second, and third pairs is connected
to the negative terminal of the DC power source 40 via a negative
terminal of the inverter 12. Each of the switching elements S*# has
a control terminal connected to the MG ECU 13.
[0043] The first current sensor 41 is provided in the V-phase cable
Cv for measuring a value, i.e. a magnitude, of a V-phase current Iv
flowing through the V-phase cable Cv. The second current sensor 42
is provided in the W-phase cable Cw for measuring a value, i.e. a
magnitude, of a W-phase current Iw flowing through the W-phase
cable Cw. Specifically, the first and second current sensors 41 and
42 are operative to cyclically output, to the IC 30, values of
first and second parameter signals, i.e. first and second analog
voltage signals Iva and Iwa; the first and second analog voltage
signals represent the measured magnitudes of the corresponding
respective V- and W-phase currents Iv and Iw.
[0044] The resolver 45 has a typical structure that includes a
power supply circuit and an excitation coil attached to the rotor
of the motor-generator 11 to be rotatable together with the rotor.
The resolver 45 also includes first and second detection coils
fixedly located to, for example, the stator of the motor-generator
11 to be magnetically linkable to the excitation coil. The first
and second detection coils are arranged to have a phase shift of 90
electric degrees therebetween.
[0045] The power supply circuit applies a sinusoidal excitation
signal, i.e. a sinusoidal AC signal, Ref to the excitation coil.
Applying the sinusoidal AC signal to the excitation coil induces a
first sinusoidal AC signal and a second sinusoidal AC signal in the
respective first and second detection coils. The rotor rotating
together with the excitation coil changes the distance between the
rotating detection coil and each of the first and second detection
coils. The distance change between the rotating excitation coil and
the first and second detection coils results in the first and
second sinusoidal AC signals whose amplitudes change depending on
the rotational angle, i.e. rotational position, of the rotor. The
first and second sinusoidal AC signals have a phase shift of 90
electrical degrees therebetween, so that the first and second
sinusoidal AC signals serve as first sinusoidal AC signal Sin and a
second cosine AC signal Cos.
[0046] The resolver 45 cyclically outputs values of the respective
sinusoidal excitation signal Ref, first sinusoidal AC signal Sin,
and second cosine AC signal Cos to the IC 30.
[0047] The IC 30 essentially includes, for example, input/output
(I/O) ports, a processing circuit, a communication circuit, and so
on. The IC 30 cyclically receives, i.e. samples, via the I/O ports,
values of the first and second analog voltage signals Iva and Iwa
from the respective first and second current sensors 41 and 42. The
IC 30 also cyclically receives, i.e. samples, via the I/O ports,
values of the respective sinusoidal excitation signal Ref, first
sinusoidal AC signal Sin, and second cosine AC signal Cos from the
resolver 45.
[0048] The MG ECU 13 is located outside the housing 12a of the
inverter 12, and the IC 30 is communicably connected to the MG ECU
13 via a communication network CN, such as a radio communication
network or a cable communication network. The communication network
CN has a predetermined communication standard, i.e. a predetermined
communication protocol, for example, in-vehicle LAN protocol, such
as controller area network protocol (CAN protocol), local
interconnect network protocol (LIN protocol), or the like.
Preferably, a communication network having a higher noise immunity,
such as a CAN network based on the CAN protocol or a LIN network
based on the LIN protocol is selected as the communication network
CN.
[0049] The IC 30 calculates, based on the sampled values of the
sinusoidal excitation signal Ref, first sinusoidal AC signal Sin,
and second cosine AC signal Cos, a rotational angle, i.e. an
electrical angle, .theta. of the rotor of the motor-generator 11 as
digital data. The IC 30 also converts sampled values of the first
and second analog voltage signals Iva and Iwa into values of first
and second digital voltage signals Ivd and Iwd. Then, the IC 30
calculates, based on the values of the first and second digital
voltage signals Ivd and Iwd, a value of a third digital voltage
signal Iud for the U-phase winding in accordance with Kirchhoff's
law.
[0050] Then, the IC 30 transforms, based on the rotational angle
.theta. of the rotor of the motor-generator 11, the values of the
first to third digital voltage signals Ivd, Iwd, and Iud into a
value of a d-axis current Id in digital format and a value of a
q-axis current Iq in digital format in the d-q coordinate system
defined relative to the rotor.
[0051] Then, the IC 30 communicates with the MG ECU 13 in
accordance with the predetermined communication protocol matching
with the communication network CN to thereby transmit the
rotational angle .theta. of the rotor of the motor-generator 11,
and the values of the respective d- and q-axis currents Id and Iq
to the MG ECU 13 via the communication network CN.
[0052] The MG ECU 13 is designed as, for example, a microcomputer
circuit. Specifically, the MG ECU 13 essentially includes, for
example, a CPU, a memory, such as a ROM and/or a RAM, an I/O, and a
bus connecting between the CPU, memory, and I/O. The MG ECU 13 can
include at least one special-purpose electronic circuit.
[0053] Specifically, the MG ECU 13 is configured such that the CPU
performs instructions of programs stored in the memory, thus
performing predetermined software tasks associated with the overall
control of the motor-generator 11. The MG ECU 13 can also be
configured such that the at least one special-purpose electronic
circuit performs predetermined hardware tasks associated with the
overall control of the motor-generator 11. The MG ECU 13 can be
configured to perform both the software tasks and the hardware
tasks associated with the overall control of the motor-generator
11.
[0054] The MG ECU 13 communicates with the IC 30 in accordance with
the predetermined communication protocol matching with the
communication network CN. The communications permit the MG ECU 13
to receive the rotational angle .theta. of the rotor of the
motor-generator 11, and the values of the d- and q-axis currents Id
and Iq to the MG ECU 13 transmitted from the IC 30 via the
communication network CN.
[0055] The MG ECU 13 controls on/off operations of the switching
elements Sup, Sun, Svp, Svn, Swp, and Swn of the switching circuit
21 based on the rotational angle .theta. of the rotor of the
motor-generator 11, the value of the d-axis current Id, and the
value of the q-axis current Iq.
[0056] For example, the MG ECU 13 compares the values of the d- and
q-axis currents Id and Iq with corresponding d- and q-axis command
current values Id* and Ice calculated based on three-phase command
current values Iu*, Iv*, and Iw*; the three-phase command current
values Iu*, Iv*, and Iw* are determined based on, for example, a
command value for at least one controlled variable of the
motor-generator 11. This comparison calculates a d-axis deviation
between the value of the d-axis current Id and the d-axis command
current value Id*, and a q-axis deviation between the value of the
q-axis current Iq and the q-axis command current value Iq*. The MG
ECU 13 performs, for example, a proportional-integral (PI)
operation using the d-axis deviation as input data, and a
proportional gain term and an integral gain term of a PI feedback
control algorithm (PI algorithm), thus calculating a command d-axis
voltage such that the d-axis deviation converges to zero. The MG
ECU 13 performs, for example, a PI operation using the q-axis
deviation as input data, and a proportional gain term and an
integral gain term of a PI feedback control algorithm, thus
calculating a command q-axis voltage such that the q-axis deviation
converges to zero.
[0057] The MG ECU 13 converts the command d-axis voltage and
command q-axis voltage into three-phase sinusoidal command voltages
using the rotational angle .theta. of the rotor. The MG ECU 13
compares in amplitude each of the three-phase sinusoidal command
voltages with a triangular PWM carrier signal having a
predetermined period corresponding to a predetermined frequency.
The MG ECU 13 generates, based on the results of the comparison,
switching signals, i.e. drive signals, for the respective switching
elements Sup, Sun, Svp, Svn, Swp, and Swn.
[0058] Each of the switching signals is, for example, a pulse
signal with a controllable duty cycle (controllable pulse width)
for a corresponding switching cycle that matches with the
predetermined period of the triangular PWM carrier signal. Then,
the MG ECU 13 transmits the switching signals to the control
terminals of the corresponding respective switching elements Sup,
Sun, Svp, Svn, Swp, and Swn, thus performing on/off operations of
the switching elements Sup, Sun, Svp, Svn, Swp, and Swn. Control of
the on/off operations of the switching elements Sup, Sun, Svp, Svn,
Swp, and Swn adjusts three-phase, i.e. U-, V-, and W-phase,
currents Iu, Iv, and Iw flowing through the respective three-phase
windings of the motor-generator 11 to the respective three-phase
command current values Iu*, Iv*, and Iw*.
[0059] In contrast, FIG. 2 schematically illustrates a current
control system 10A for the motor 11 according a comparative example
of this embodiment. The structure and functions of the current
control system 10A according to the comparative example are mainly
different from the current control apparatus 10 according to this
embodiment by the following points. So, identical parts between the
comparative example and this embodiment, to which identical
reference characters are assigned, are omitted or simplified to
avoid redundant description.
[0060] The current control system 10A includes an IC 30A and a MG
ECU 13A in place of the IC 30 and the MG ECU 13.
[0061] The IC 30A cyclically receives, i.e. samples, via the I/O
ports, values of the respective first and second analog voltage
signals Iva and Iwa input thereto from the respective first and
second current sensors 41 and 42, and converts the values of the
respective first and second analog voltage signals Iva and Iwa into
values of first and second digital voltage signals Ivd and Iwd.
[0062] The IC 30A communicates with the MG ECU 13A in accordance
with the predetermined communication protocol matching with the
communication network CN to thereby transmit the values of the
first and second digital voltage signals Ivd and Iwd to the MG ECU
13A via the communication network CN.
[0063] The MG ECU 13A communicates with the IC 30A in accordance
with the predetermined communication protocol matching with the
communication network CN. The communications permits the MG ECU 13A
to receive the values of the first and second voltage signals Ivd
and Iwd transmitted from the IC 30A via the communication network
CN.
[0064] In addition, the MG ECU 13A cyclically receives, i.e.
samples, values of the respective sinusoidal excitation signal Ref,
first sinusoidal AC signal Sin, and second cosine AC signal Cos
input thereto from the resolver 45. The MG ECU 13A calculates,
based on the sampled values of the sinusoidal excitation signal
Ref, first sinusoidal AC signal Sin, and second cosine AC signal
Cos, a rotational angle, i.e. an electrical angle, .theta. of the
rotor of the motor-generator 11 in digital format. The MG ECU 13A
also calculates, based on the values of the first and second
digital voltage signals Ivd and Iwd, a value of a third digital
voltage signal Iud in digital format for the U-phase winding in
accordance with Kirchhoff's law.
[0065] Then, the MG ECU 13A transforms, based on the rotational
angle .theta. of the rotor of the motor-generator 11, the values of
the first, second, and third digital voltage signals Ivd, Iwd, and
Iud into a value of a d-axis current Ida in digital format and a
value of a digital q-axis current Iqa in digital format in the d-q
coordinate system defined relative to the rotor.
[0066] Precise transformation of values of the d- and q-axis
currents Ida. and Iqa in digital format in the d-q coordinate
system necessitates that values of the V- and W-phase currents Iv
and Iw, which are measured by the first and second current sensors
41 and 42 at time t1, is synchronized with a rotational angle of
the rotor, which is measured by the resolver 45 at the same time t1
(see FIG. 4).
[0067] Referring to FIG. 3, the resolver 45 of the current control
apparatus 10A is configured to transmit values of the respective
sinusoidal excitation signal Ref, first sinusoidal AC signal Sin,
and second cosine AC signal Cos every predetermined cycle Ta1. In
other words, the MG ECU 13A is configured to sample values of the
respective sinusoidal excitation signal Ref, first sinusoidal AC
signal Sin, and second cosine AC signal Cos from the resolver 45
every predetermined cycle Ta1. The values of the respective
sinusoidal excitation signal Ref, first sinusoidal AC signal Sin,
and second cosine AC signal Cos are finally converted into a
corresponding rotational angle .theta. of the rotor by the MG ECU
13A, so that the cycle Ta1 represents a cycle of measurement of the
rotational angle .theta. of the rotor. The cycle Ta1 is previously
determined according to the period of the triangular PWM carrier
signal. For example, FIG. 3 shows that the cycle Ta1 is
substantially set to half of the period of the triangular PWM
carrier signal.
[0068] In addition, the IC 30A is configured to sample values of
the respective first and second analog voltage signals Iva and Iwa
input thereto from the respective first and second current sensors
41 and 42 every predetermined cycle Ta2; the cycle Ta2 is set to
be, for example, longer than the cycle Ta1. The IC 30A is also
configured to convert the sampled values of the respective first
and second analog voltage signals Iva and Iwa into values of first
and second digital voltage signals Ivd and Iwd in digital format,
and transmit the values of the first and second digital voltage
signals Ivd and Iwd to the MG ECU 13A via the communication network
CN.
[0069] That is, let us assume that
[0070] (1) A cyclic sampling timing, by the MG ECU 13A, of values
of the respective sinusoidal excitation signal Ref, first
sinusoidal AC signal Sin, and second cosine AC signal Cos from the
resolver 45 will be referred to as a first cyclic sampling
timing
[0071] (2) A cyclic sampling timing, by the IC 30A, values of the
respective first and second analog voltage signals Iva and Iwa
input thereto from the respective first and second current sensors
41. and 42 will be referred to as a second cyclic sampling
timing
[0072] (3) The first cyclic sampling timing is synchronized with
the second cyclic sampling timing.
[0073] Even if the assumption is satisfied, the analog-digital
conversion process and the communication process carried out by the
IC 30A delays, by a certain amount of time, a sampling timing of
the values of the first and second voltage signals Ivd and Iwd to
the MG ECU 13A with respect to a corresponding sampling timing of
values of the respective sinusoidal excitation signal Ref, first
sinusoidal AC signal Sin, and second cosine AC signal Cos to the MG
ECU 13A.
[0074] In other words, the structure of the current control
apparatus 10A results in a sampling timing of the values of the
first and second voltage signals Ivd and Iwd to the MG ECU 13A
being asynchronous to a corresponding sampling timing of values of
the respective sinusoidal excitation signal Ref, first sinusoidal
AC signal Sin, and second cosine AC signal Cos to the MG ECU
13A.
[0075] As described above, the MG ECU 13A transforms, based on the
rotational angle .theta. of the rotor of the motor-generator 11,
the values of the first, second, and third digital voltage signals
Ivd, Iwd, and Iud into a value of the d-axis current Ida and a
value of the q-axis current Iqa in the d-q coordinate system
defined relative to the rotor. Thus, the sampling-timing
asynchronicity may result in a phase shift of a current vector Va
(Ida, Iqa) of the values of the d- and q-axis currents Id and Iq in
the d-q-coordinate system with respect to a current vector V (Id,
Iq) that is obtained when no sampling-timing asynchronicity occurs
(see FIG. 5).
[0076] In contrast, the IC 30 of the current control apparatus 10
according to this embodiment is configured to synchronize a
sampling timing of the values of the first and second analog
voltage signals Iva and Iwa thereto and a corresponding sampling
timing of values of the respective sinusoidal excitation signal
Ref, first sinusoidal AC signal Sin, and second cosine AC signal
Cos thereto. This means that values of the V- and W-phase currents
Iv and Iw, which are measured by the first and second current
sensors 41 and 42 at time t1, is synchronized with a rotational
angle of the rotor, which is measured by the resolver 45 at the
same time t1 (see FIG. 4).
[0077] FIG. 6 schematically illustrates a block diagram
schematically illustrating functional modules included in the IC
30; these functional modules are implemented by, for example, the
I/O ports, the processing circuit, and the communication circuit of
the IC 30. The IC 30 can include hardware modules functionally
matching with the functional modules illustrated in FIG. 6 or
hardware-software hybrid modules functionally matching with the
functional modules illustrated in FIG. 6.
[0078] Referring to FIG. 6, the IC 30 includes a first A/D
converter 31A, a second A/D converter 31B, a third A/D converter
31C, a resolver/digital converter (R/D converter) 32, a two-phase
current calculator 33, a communication unit 34, and a
synchronization controller 35.
[0079] The synchronization controller 35 is operatively connected
to the first current sensor 41, the second current sensor 42, and
the resolver 45. The synchronization controller 35 controls the
first current sensor 41, the second current sensor 42, and the
resolver 45 such that
[0080] (1) The first current sensor 41 measures a magnitude of the
V-phase current in a predetermined cycle Ta3, and outputs a value
of the first analog voltage signal Iva representing the measured
magnitude of the V-phase current to the IC 30
[0081] (2) The second current sensor 42 measures a magnitude of the
W-phase current in the predetermined cycle Ta3 in synchronization
with measurement of a magnitude of the V-phase current by the first
current sensor 42
[0082] (3) The resolver 45 measures the first sinusoidal AC signal
Sin and second cosine AC signal Cos, and outputs values of the
respective sinusoidal excitation signal Ref, first sinusoidal AC
signal Sin, and second cosine AC signal Cos to the IC 30 in the
predetermined cycle Ta3 in synchronization with measurement of a
magnitude of each of the V- and W-phase currents by a corresponding
one of the first and second current sensors 41 and 42.
[0083] For example, a value of the first analog voltage signal Iva
increases in proportion to an increase of a measured magnitude of
the V-phase current. Similarly, a value of the second analog
voltage signal Iwa increases in proportion to an increase of a
measured magnitude of the W-phase current.
[0084] The A/D converter 31B receives, i.e. samples, a value of the
first analog voltage signal Iva sent from the first current sensor
41 in the predetermined cycle Ta3, and converts the value of the
first analog voltage signal Iva into a value of the first digital
voltage signal Ivd in digital format.
[0085] The A/D converter 31C receives, i.e. samples, a value of the
second analog voltage signal Iwa sent from the second current
sensor 42 in the predetermined cycle Ta3, and converts the value of
the second analog voltage signal Iwa into a value of the second
digital voltage signal Iwd in digital format.
[0086] Each of the A/D converters 31B and 31C outputs the value of
a corresponding one of the first and second voltage signals Ivd and
Iwd in digital format to the two-phase current calculator 33.
[0087] The A/D converter 31A receives, i.e. samples, values of the
respective sinusoidal excitation signal Ref, first sinusoidal AC
signal Sin, and second cosine AC signal Cos in the predetermined
cycle Ta3. Then, the A/D converter 31A converts the values of the
respective sinusoidal excitation signal Ref, first sinusoidal AC
signal Sin, and second cosine AC signal Cos into values of digital
signals REF, SIN, and COS. The A/D converter 31A outputs the values
of the digital signals REF, SIN, and COS to the RID converter
32.
[0088] That is, the synchronization controller 35 and the A/D
converters 31A to 31C serve as a synchronizing unit, i.e.
synchronizing means, for synchronizing a measurement timing, i.e. a
sampling timing, of values of the first and second analog voltage
signals Iva and Iwa from the motor-generator 11 with a measurement
timing, i.e. a sampling timing, of the first sinusoidal AC signal
Sin and second cosine AC signal Cos from the motor-generator
11.
[0089] The R/D converter 32 has a typical structure that includes a
cosine multiplier, a sine multiplier, a low-pass filter, and so on.
Specifically, the R/D converter 32 receives the values of the
digital signals REF, SIN, and COS. Then, the R/D converter 32
performs predetermined calculations based on the received values of
the digital signals SIN and COS and synchronized detection based on
the value of the digital signal REF, thus converting the digital
signals SIN and COS into a rotational angle, i.e. an electrical
angle, .theta. of the rotor of the motor-generator 11 in digital
format. Then, the R/D converter 32 outputs the rotational angle
.theta. of the rotor of the motor-generator 11 to the two-phase
current calculator 33.
[0090] The two-phase current calculator 33 calculates the values of
the first and second digital voltage signals Ivd and Iwd, a value
of the third digital voltage signal Iud for the U-phase winding in
accordance with Kirchhoff's law.
[0091] Then, the two-phase current calculator 33 transforms, based
on the rotational angle .theta. of the rotor of the motor-generator
11, the values of the first to third digital voltage signals Ivd,
Iwd, and Iud into a value of the d-axis current Id in digital
format and a value of the q-axis current Iq in digital format in
the d-q coordinate system defined relative to the rotor. For
example, the two-phase current calculator 33 has map data or
equation data. The map data or equation data represents
correlations between values of the first to third digital voltage
signals Ivd, Iwd, and Iud, values of the d- and q-axis currents,
and values of the rotational angle 8 of the rotor. Thus, the
two-phase current calculator 33 refers to the map data or equation
data using the values of the first to third digital voltage signals
Ivd, Iwd, and Iud and the rotational angle .theta. of the rotor.
Based on the results of the reference, the two-phase current
calculator 33 extracts values of the d- and q-axis currents that
match with the values of the first to third digital voltage signals
Ivd, Iwd, and Iud and the rotational angle of the rotor.
Thereafter, the two-phase current calculator 33 outputs the
extracted values of the d- and q-axis currents and the rotational
angle .theta. of the rotor to the communication unit 34.
[0092] The communication unit 34 communicates with the MG ECU 13 in
accordance with the predetermined communication protocol matching
with the communication network CN to thereby transmit the
rotational angle .theta. of the rotor of the motor-generator 11,
and the values of the respective d- and q-axis currents Id and Iq
to the MG ECU 13 via the communication network CN.
[0093] As described above, the MG ECU 13 receives the rotational
angle .theta. of the rotor, and the values of the d- and q-axis
currents Id and Iq based on communications with the IC 30 via the
communication network CN. Then, the MG ECU 13
[0094] (1) Calculates a command d-axis current and a command q-axis
current based on the received rotational angle .theta. of the
rotor, and the values of the d- and q-axis currents Id and Iq
[0095] (2) Converts the command d-axis voltage and command q-axis
voltage into three-phase sinusoidal command voltages using the
rotational angle .theta. of the rotor and the predetermined PWM
carrier signal
[0096] (3) Generates, based on the results of comparison between
the three-phase sinusoidal command voltages and the PWM carrier
signal, switching signals for the respective switching elements
Sup, Sun, Svp, Svn, Swp, and Swn, thus controlling on/off
operations of the switching elements Sup, Sun, Svp, Svn, Swp, and
Swn based on the respective switching signals.
[0097] These operations of the MG ECU 13 adjust the three-phase,
i.e. U-, V-, and W-phase, currents Iu, Iv, and Iw flowing through
the respective three-phase windings of the motor-generator 11 to
the respective three-phase command current values Iu*, Iv*, and
Iw*.
[0098] FIG. 7 schematically illustrates measurement timings, i.e.
sampling timings, of values of the first and second analog voltage
signals Iva and Iwa from the motor-generator 11, and measurement
timings, i.e. sampling timings, of values of the respective
sinusoidal excitation signal Ref, first sinusoidal AC signal Sin,
and second cosine AC signal Cos from the motor-generator 11.
[0099] Specifically, the IC 30
[0100] (1) Samples a value of each of the first and second analog
voltage signals Iva and Iwa in the predetermined cycle Ta3 from the
motor-generator 11.
[0101] (2) Samples values of the respective sinusoidal excitation
signal Ref; first sinusoidal AC signal Sin, and second cosine AC
signal Cos in the predetermined cycle Ta3 from the motor-generator
11 in synchronization with sampling of a value of each of the first
and second analog voltage signals Iva and Iwa (see MEASUREMENT OF
ROTATIONAL ANGLE OF ROTOR in FIG. 7).
[0102] Note that the IC 30 is capable of setting the predetermined
cycle Ta3 to a constant value independently of the period of the
PWM carrier signal, or changing the predetermined cycle Ta3
depending on change of the period of the PWM carrier signal. For
example, the IC 30 is capable of decreasing the cycle Ta3 with a
decrease of the period of the PWM carrier signal.
[0103] As described above, the current control system 10
synchronizes each sampling timing of values of the first and second
analog voltage signals Iva and Iwa from the motor-generator with a
corresponding sampling timing of values of the respective
sinusoidal excitation signal Ref, first sinusoidal AC signal Sin,
and second cosine AC signal Cos in the predetermined cycle Ta3 from
the motor-generator 11.
[0104] This synchronization results in calculation of values of the
d- and q-axis currents according to this embodiment with higher
accuracy in comparison to calculation of those of the d- and q-axis
currents according to the comparison example in which each sampling
timing of values of the first and second analog voltage signals Iva
and Iwa from the motor-generator 11 is asynchronous with a
corresponding sampling timing of values of the respective
sinusoidal excitation signal Ref, first sinusoidal AC signal Sin,
and second cosine AC signal Cos.
[0105] The IC 30 of the current control system 10 is configured to
transmit the rotational angle .theta. of the rotor of the
motor-generator 11, and the values of the respective d- and q-axis
currents Id and Iq to the MG ECU 13 via the communication network
CN in accordance with the predetermined communication protocol.
This configuration instructs the MG ECU 13 to control on/off
operations of the switching elements Sup, Sun, Svp, Svn, Swp, and
Swn, thus adjusting the three-phase currents Iu, Iv, and Iw flowing
through the respective three-phase windings of the motor-generator
11 to the respective three-phase command current values Iu*, Iv*,
and Iw*.
[0106] Thus, even if the current control apparatus 10 is configured
to transmit the values of respective d- and q-axis currents Id and
Iq to the MG ECU 13 in accordance with the predetermined
communication protocol, the current control apparatus 10 results in
proper control of the three-phase currents Iu, Iv, and Iw flowing
through the respective three-phase windings of the motor-generator
11.
[0107] The current control apparatus 10 uses a commercially
available resolver 45 as a rotational angle sensor, and the IC 30
is provided with the R/D converter 32 that converts values of the
respective sinusoidal excitation signal Ref, first sinusoidal AC
signal Sin, and second cosine AC signal Cos measured by the
resolver 45 from the motor-generator 11 into the rotational angle
.theta. of the rotor of the motor-generator 11. That is, the A/D
functions of values of the first and second analog voltage signals
Iva and Iwa measured by the respective current sensors 41 and 42
and the R/D functions of values of these analog signals Ref, Sin,
and Cos into a digital rotational angle .theta. of the rotor of the
motor-generator 11 are integrated in the IC 30. This integration
simplifies the circuit configuration of the current control
apparatus 10.
[0108] The current control apparatuses 10 according to this
embodiment can be modified at least as follows.
[0109] The current control apparatus 10 according to this
embodiment uses the resolver 45 as a rotational angle sensor, but
can use another type rotational angle sensor, such as an optical or
a magnetic encoder.
[0110] The current control apparatus 10 is equipped with the first
and second current sensors 41 and 42 for outputting the first and
second parameter signals representing measured magnitudes of the
respective V- and W-phase currents Iv and Iw, but the present
disclosure is not limited thereto, Specifically, the current
control apparatus 10 can be provided with, in addition to the first
and second current sensors 41 and 42, a third current sensor for
measuring the magnitude of the U-phase current Iu flowing through
the U-phase winding, and outputting a third parameter signal
representing the measured magnitude of the U-phase current Iu.
[0111] As the motor-generator 11, a typical motor or a power
generator, such as an alternator, can be used. The motor-generator
11 is designed as a permanent magnet synchronous motor-generator,
but can be designed as an induction motor or another type of
synchronous motor,
[0112] The IC 30 is configured to transmit digital signals to the
MG ECU 13 located outside the housing 12a of the inverter 12 via
communications with the MG ECU 13, but can be configured to
transmit digital signals to the MG ECU 13 located outside the
package of the IC 30 via communications with the MG ECU 13.
[0113] The R/D converter 32 has a function of receiving values of
the digital signals REF, SIN, and COS, and performs predetermined
calculations based on the received values, thus converting the
digital signals SIN and COS into a rotational angle .theta. of the
rotor of the motor-generator 11 in digital format. The present
disclosure is however not limited to the structure of the R/D
converter 32. Specifically, the R/D converter 32 can be configured
to generate the sinusoidal excitation signal, and apply the
sinusoidal excitation signal to the excitation coil. In this
modification, the resolver 32 does not need to transmit the
excitation signal to the R/D converter 32. The R/D converter 32 can
also have a function of the A/D converter 31A.
[0114] The synchronization controller 35 is provided separately
from the A/D converters 31A to 31C, although the present disclosure
is not limited thereto. Specifically, at least one of the A/D
converter 31A to 31C includes such a synchronization controller 35
for synchronizing a measurement timing, i.e. a sampling timing, of
values of the first and second analog voltage signals Iva and Iwa
from the motor-generator 11 with a measurement timing, i.e. a
sampling timing, of the first sinusoidal AC signal Sin and second
cosine AC signal Cos from the motor-generator 11.
[0115] While an illustrative embodiment of the present disclosure
has been described herein, the present disclosure is not limited to
the embodiment described herein, but includes any and all
embodiments having modifications, omissions, combinations (e.g., of
aspects across various embodiments), adaptations and/or
alternations as would be appreciated by those in the art based on
the present disclosure. The limitations in the claims are to be
interpreted broadly based on the language employed in the claims
and not limited to examples described in the present specification
or during the prosecution of the application, which examples are to
be construed as non-exclusive.
* * * * *